1. Field of the Invention
The present invention relates to a relatively compact portable cooler operative by utilizing the endothermic and exothermic phenomenon pertaining to a chemical reaction.
2. Description of the Prior Art
Various attempts have been made to realize a system which performs a cooling cycle, heating cycle, etc. by utilizing the endothermic and exothermic phenomenon pertaining to a chemical reaction. This system has the function of accumulating heat, cooling, carburetion and raising temperature and, therefore, is generally called as a chemical heat pump. One such known system is disclosed in Japanese Patent Laid-open Publication No. 59-104057, which comprises, as re-illustrated here in FIG. 4, two vacuum vessels 31, 33, an absorbent 32 disposed in the vessel 31 for reversibly absorbing and discharging a heat-transfer medium in the vapor phase, a fluid heat-transfer medium 34, a valve unit 36, and a connecting pipe 37 interconnecting the vessels 31, 32 and adapted to be opened and closed by the valve unit 36. In the operation of this system, the vessels 31, 33 are evacuated by a vacuum pump (not shown) and subsequently the valve unit 36 is opened whereupon the fluid heat-transfer medium 34 in the evacuated or vacuum vessel 33 evaporates. The heat-transfer medium 34 exits the vessel 33 in the vapor phase, then passes through the connecting pipe 37 and enters the evacuated vacuum vessel 31 where it reacts with the absorbent 31. In this instance, the vacuum vessel 33 extracts or absorbs heat from the ambient air by the evaporation of the fluid heat-transfer medium 34 and thereby lowers the temperature. The heat thus absorbed can be used for cooling purposes. On the other hand, the vacuum vessel 31 releases or liberates heat to the ambient air by the reaction between the heat-transfer medium 34 and the absorbent 32 and thereby raises the temperature. The heat thus liberated can be used for heating purposes. After the reaction completes, the vacuum vessel 31 is heated for regeneration, thereby restoring the entire system to the original state. Thus, the endothermic and exothermic phenomenon pertaining to a chemical reaction is used for the purpose of cooling, heating and the like. The chemical reaction used in the disclosed chemical heat pump is absorption, however, any other suitable reaction system such as addition, hydration, adsorption, etc. may be used in compliance with the intended purpose.
Various cooling/heating equipment using such chemical reactions have been proposed heretofore, however, most of them have not yet been put into practical use for some reasons. One reason is that the proposed cooling/heating equipment are large in size and heavy in weight. As described above with reference to FIG. 4, the prior system includes, as essential components, two vessels, a passage interconnecting the vessels and a valve unit disposed in the passage. Each of the vessels further requires a heat-exchange means for promoting the reaction. In the case where the working medium comprises water, the inside of the system forms nearly a perfect vacuum because the vapor pressure of water around the room temperature is about several to several tens Torr. This means that the passage and the valve unit must have a large opening area so as to minimize pressure losses when the working medium passes through them in the vapor phase. The entire system having such passage and valve unit is large in size and expensive to manufacture.